Against 2d6

The players from my Classic Traveller one-shot last week started asking whether there would be more adventures for those characters.  I felt a certain unease at the prospect, and decided to examine it.

I think I really dislike 2d6 as a core resolution mechanic, and "fighting with" the dice last session reminded me why.

The central tendency is very strong.  You get many results right in the middle of the range, and small modifiers can change the probability of success dramatically when the target number is close to the center of the range.  The total range is also quite small (2-12), so it really doesn't take that many small modifiers stacking up to make success or failure all but certain.  This is the same problem that ACKS 1e ran into with stacking up modifiers to reaction rolls, except that every piece of Traveller is susceptible to this failure-mode.  This was one nice thing about Thousand Suns' move to 2d12 - it becomes much harder for modifiers to completely dominate randomness (apparently I wrote a draft post of a review of Thousand Suns back in 2015 but never published it - oops).

In theory, many Classic Traveller skill rolls have modifiers from attributes and skill level laid out in the text, under the description of the skills.  However, in a time-constrained after-work session, digging out the skill descriptions for every roll is prohibitively time-expensive.  Even in a longer session, it stalls the tempo.  So I am inclined to improvise target numbers.  In an OSR game without a skill system, I would pick probabilities which sound reasonable within the game-world and negotiate with the players.  "That sounds pretty challenging, maybe a 20% chance of success"  "I'm very strong though."  "OK, 35% - give me a 14+ on a d20".  Translating intuitive probabilities of success into 2d6 target numbers is a huge pain, and the central tendency means that there is very little room for fine-grained distinctions between target numbers in the middle of the range.  You go from 72% chance of success on 6+ to 58% chance of success on 7+ to 42% on 8+.  You can only draw fine-grained distinctions out at the edges of the range (11+ vs 12+, for example; 8% vs 3%).  Even there, the granularity of target numbers is no finer than a d20's.

I think the only real virtues of 2d6 systems are that the player-facing math is easy (almost no significant two-digit operations - if your roll plus skill get into two digits, success is a foregone conclusion) and that d6s are easy to come by.  I have heard, apocryphally, that when Gygax first learned of d20s, he went "This changes everything!"  Having returned briefly to pure-d6 gaming, I can see why.

And this all makes me sad, because I have fond memories of Traveller, but man, actually running games on 2d6 kinda sucks.  It's a pity that Traveller d20 was such a poor port (tangentially, I'm shocked that T20 has such good reviews on DriveThru; maybe I should write a dissenting one).

I feel like converting Traveller to just use d20s (and not also importing the rest of the "d20 System"s baggae like T20 did) wouldn't be hard, exactly - just a slog.

Classic Traveller One-Shot Reflections

I ran a one-shot of Classic Traveller at the office after work last night.  The players crewed a Far Trader carrying a contract cargo across six parsecs, with one intermediate system being a very-low population law level 0 asteroid habitat and the other being a balkanized world with a pirate problem.  This gave us an opportunity to have one ground combat (with the "customs officials" from the asteroid habitat after the players docked to deliver a contract cargo and buy fuel) and one starship combat (with a pirate Far Trader in the balkanized system).

Sadly I did not end up running either combat by Rules-as-Written.  Having ground combat with the "customs officials" inside the starship was more of a Snapshot/Azhanti High Lightning-situation than one where abstract range bands were appropriate, and I ended up falling back to almost a B/X-style "move n squares and then attack or take other non-attack action" turn pattern.  I also used ACKS-style countdown initiative rolled per individual per round.  I did resolve attacks and damage per CT though (or as closely as I understood it).  Having all three of weapon-vs-armor, weapon range, and per-weapon ability-score modifier DM tables was...  a bit much, as a referee trying to abstract all that away from the players.  I did like the lack of adding degree of success to damage rolls like Mongoose 1e does, which meant that calculating the exact degree of success was not important.  Allocating each die of damage to an ability score was also interesting; I ended up in a couple situations going "OK I don't think there's an allocation here where this guy can remain conscious / not-severely-injured".  For the most part it was a "shotguns and SMGs vs cloth armor at close range" combat and characters felt fairly fragile.  The lack of damage reduction from Mongoose-style armor meant that if you took a 4d6 shotgun hit, there was a good chance you were going unconscious.  I could definitely see how higher-damage weapons like from Mercenary could make combat very lethal; if your armor gets penetrated by a 6d6 weapon, you're dead on average.

For the starship combat, there was no way that our conference room table was going to work for full-detail CT Book 2 vector movement with tape measures.  I ended up going with more abstract range-band combat in the Mongoose style.  I messed up pulse laser damage (per the errata, they have -1 to hit and do double damage - so a double-turret pulse laser hit should've been four damage rolls rather than the two I was doing).  Needing Gunner Interact to apply your Gunnery skill is kinda painful, and the Maneuver/Evade programs giving a tiny fraction of Pilot skill as an evasion bonus makes them hard to justify over Auto/Evade.  I do think there's the core of a fun minigame in computer program selection, but having the lack of compute for certain options basically shut down certain character roles felt a bit bad.  Overall I felt like this space combat dragged a bit but maybe it would've been more decisive with errata'd pulse laser damage.  The 9+ target and no attribute DMs for damage control was also rough.  I also mistook the "Hold" result on the damage table for "Hull"; I expected it to say something more like "Cargo".  Maybe my vision is starting to give out.

I'm not sure to what extent switching to Mayday would've helped (or Mayday plus CT's damage table including stuff like Hold).  It looks like Mayday programs are a bit less terrible (like Maneuver/Evade just giving a flat DM).  I think disengaging from combat to a planet's surface might also have been more viable under Mayday than under abstract ranges.

I did end up using the character generation systems from the High Guard, Merchant Prince, Scouts, and Citizens of the Imperium (for a belter) supplements for pregens.  Ultimately I think that I like that the expanded chargen systems from the supplements are more forgiving for survival and enlistment rolls and skills per term, but they still feel low-choice vs Mongoose's three paths per career.  It is still difficult to target certain skills; with one of the characters I was fishing for Medical on Merchant's Prince's Purser->Medic track but got re-assigned to Sales during my first term.  Attributes feel less important in the supplementary character generation systems than in Book 1 chargen; many of the career sub-tracks don't get DMs to survival and promotion throws from attributes, just from having certain skills at certain levels.  I think this might be for the better though; it makes playing 2d6-in-order a lot more viable.

Overall it sounded like the players still had fun.  One player who had never played an RPG before sounded happy.  One player who had played Mongoose Traveller 2e was puzzled at the choice of Classic (which is fair) and complained of a lack of weapon variety (which was more puzzling; seemed to me less of a problem with the system than with my picking a handful of weapons that seemed appropriate for circumstances).  Several were curious about turning it into a campaign, but I worry that I gave them too many opportunities for profit and they will have quite a bit of starting capital if I have to live with the consequences of that.  I guess they have a lot of damage from the starship combat that I would need to figure the costs on, which could soak up a big pile of cash.

I had grand ambitions about giving the party more choices of routes from the starting point to the contract destination, but discarded a couple of worlds as I ran out of time to prep interesting encounters for them and ended up with a minimal, linear path.  I had also thought it would be fun to generate like ten pregens, give the resumes to the Captain, and have him choose which four to hire, but it turns out that generating pregens with the supplementary chargen systems takes a long time and I only ended up making as many as I needed.  I also gave each pregen a secret (generally a side objective with a monetary payout for completion and a couple pieces of equipment in their bags unknown to the rest of the crew) and these were a mixed success.  I had kind of expected players to get out laptops and start communicating in secret, in a Braunstein kind of style, which would have allowed more shenanigans, but they were pretty studiously disconnected from their electronics!  What a problem to have!  I think the very tight weeknight one-shot timeframe precluded the sort of downtime for intrigue that would've made that work better.  Probably I was trying to do too many things at once here; fitting a ground combat *and* a space combat *and* some speculative trading / ship finance management *and* some intra-party intrigue into a three-hour-session in a somewhat-unfamiliar system was a lot.  I should probably consider myself fortunate that it went as well as it did.

Playing with Classic Traveller Book 1 Chargen

Spent some time this morning generating characters from CT Book 1, intending to use them as pregens for a game in the office.

The inability to follow up a career where you failed to reenlist with another career makes for many more low-term characters than I recall seeing in Mongoose.

I don't think we ever rolled stats in order in Mongoose either.  Given the smaller set of careers, if there's something in particular that the party still "needs", fishing it out is much more challenging.

Intelligence seems, if not "king" of the attributes during character generation, at least very widely applicable.  The only career that doesn't get some sort of benefit for good Int is Army, and Merchants rely almost exclusively on Int.  Navy and Marines both have high thresholds for bonuses, and Marines have the widest set of stats to get bonuses from (ye olde Multiple Ability Score Distribution).

Just under half of the characters I generated died, mostly in their first term after a failed enlistment roll and then drafting into a service where they had no bonuses to survival.

The Other career seems terrible.  If you have the Int for the survival bonus, you also have the Int to go Merchant and pick up rank for extra skill and benefit rolls.  It's funny that the "two skills per term" on the Scout is justified with their lack of promotion, but Other doesn't have ranks or double skills.  I guess the play with Other is to hope for Gambling and the 100k cash roll.  It's on both of their skill tables that aren't Edu gated, and you don't really want to be rolling on Personal Development because the -1 Soc result is worse than nothing.

I was surprised at how hard it has been to fish out Pilot, Engineering, and Computer.  You basically need to be high-Edu Navy, Scout, or Merchant, and neither Scout nor Merchant reward Edu in their career throws.  Leader and Admin are likewise locked behind high Edu.

I had previously been pretty skeptical of the expanded character generation rules from eg Mercenary and High Guard.  They seemed like power creep, but having spent more time with the Book 1 rules, I can definitely see the appeal of the college-type options to guarantee access to certain important skills like Medic and Pilot, as well as access to the Advanced Education skills table.

The aging table also kicks in much more aggressively than in Mongoose; you probably lose 1-2 points of physical attributes after each of terms 4-6, whereas in Mongoose you might get unlucky and lose a couple points after one of those terms but it was inconsistent until you hit 6-7 terms.  In Mongoose after the 4th term you have a 1 in 36 chance of losing 1 point from each physical attribute; in CT that chance of losing 1 point from each physical attribute after your 4th term is like 15%.  In Mongoose after your 4th term your odds of not taking any aging penalties are like 80%; in CT after your 4th term your odds of not taking any aging penalties are closer to 10%.  And no anagathics during chargen like Mongoose.

So between stats in order making enlistment and survival rolls tougher, and harsher aging penalties, I suspect characters probably end up skewing younger under good play.  You're definitely going to pay stats for those terms 4-6 in a way that you probably didn't in Mongoose.  Lack of enlisted ranks combined with shorter careers also makes for fewer rolls for benefits.

I still don't have a workable-looking pregen party with a broad skill distribution, because my dice hate rolling high Edu apparently.  But at least I learned some things.

Traveller: Knight-Captains

I read Space Viking in December and meant to blog about it but there has been a lot of other reading to blog about lately.  It was very useful context for understanding Traveller's idea of Feudal Technocracy.  The Sword Worlders in Space Viking have planetary kings, continental dukes, and counts of what sound like large industrial conglomerates.  This is obviously somewhat different than what Traveller seems to expect of eg subsector dukes, but it's an interesting idea.

The bottom end of nobility, though, feels a bit underdeveloped in both cases.  If your counts own large corporations, what do your knights own?

Maybe small businesses.  Maybe well-armed small businesses which can be called upon by their lords for military service.  Like far traders with triple turrets, or a mercenary unit.  And really, if you don't have the central authority to keep weapons out of the hands of your people, getting oaths of fealty and to uphold your laws from at least the ones organizing groups of armed men sounds like a reasonable policy from a sovereign's perspective...

There's a certain charm to the idea of "Finished your fourth term in the Navy with a SOC of 12?  You have received word that your eldest uncle passed away, and you are heir to your family's ship.  Arise, Sir Sigismund of the Far Trader Beowulf."  I've heard worse excuses for giving the party a ship.

I don't think that doing this, even in the absence of a starship loan, necessarily removes the financial tension from the game; she's an old, old ship, been in the family for generations, and has lots of quirks and needs lots of maintenance.  The nobility was often in debt historically; you have noblesse oblige to those under you, expenses to keep up appearances and to maintain your status among your peers, and when your lord calls, you must go, even if there may not be profit in the trip.

And then your third cousin shows up to press his claim to the family ship and you have to settle the matter in a gentlemanly fashion, which is to say, dueling.

...  I wonder if there are any good bits to lift from Pendragon or Wolves of God for something like this.

Classic Traveller: Dark Nebula

 

Continuing my read-through of the Classic Traveller wargames, Dark Nebula was published in 1980 and covers a war between the Solomani and the Aslan over about two subsectors of space, including one difficult-to-traverse nebula.  Turns are two years of in-universe time, each hex is half a parsec, naval units represent individual ships, and ground units are divisions.

Overall the core of this game looks pretty reasonable.  The space combat system is kinda neat.  The defender nominates a ship, the attacker chooses one of their ships to engage it, and then this repeats until one side is out of uncommitted ships, at which point the side with more ships left uncommitted can assign them as they please to the various 1:1 ship combats already committed to.  Once ships are matched up, the resolution of each of these combats looks pretty straightforward.

I think what I like about this fleet combat design is that there are lots of significant choices (what order to nominate and assign your ships in) but little mechanical complexity.  In general this seems like a desirable property in a game.  And at the scale this game is operating at, "where do you assign which assets" probably is the right question to be posing to players.

I'm also tickled by the inclusion of tanker-ships, really mobile refineries that you can park in systems without gas giants to skim hydrogen off of the star and refine it into fuel, allowing that system to be traversed by other ships without delays.  I love me some logistics-infrastructure-construction.

One thing here that I found a bit surprising was that moving ships can move as far as they want on the hex maps as long as they're moving along jump routes between systems with fuel available, until they enter a system that lacks fuel or where there's an enemy presence (or is in the nebula and requires exploration).  It makes some sense under the time-per-turn assumptions and the scale of the map, but "move as far as you want" still made me stop and think.  It almost has a railroad-war feeling, like the American Civil War or World War 1, rather than an open-water naval warfare feeling.  Maybe that's always been true of naval warfare under Traveller's assumptions and I just never realized it.

There are a couple of other surprising things in Dark Nebula.  It feels like a somewhat experimental game; there's tech progress from research in the titular nebula, semi-randomized initial boardstate due to the map placement procedure, and neutral forces with reaction rolls, potentially hostile or potentially hireable.  I definitely didn't expect randomization of map layout in a Traveller game set in the Third Imperium continuity.  Some weirdness arises from this - the maps have hex numbers seemingly from a much bigger hexmap, which are very unlikely to end up getting put together into a sensible order during the alternating placement procedure.  I appreciate that the scan quality is good enough to read the hex numbers though!

There are also a couple of other things about the maps which are weird, and not in a great way.  The star density on them is rather lower than is typical for Traveller.  Several of these quarter-subsector maps only have four stars in them, and the densest have eight.  In a typical Traveller subsector, I'd expect more like 40 systems, or 10 per average map on this scale.  I'm not sure how well the balance of unit production against destruction would scale up to higher-density maps and owning more planets.  Also, having a much higher-density graph of systems might lose some of that railroad-war feel and change the character of the game significantly.  Finally, the way Dark Nebula handles ground forces on planets is that there's a box in an empty hex adjacent to each inhabited system, representing the surface of the planet, and you put troop counters there.  But this would not scale well to higher-density maps.  The quality of infrastructure in these inhabited systems is also denoted by the color of the planet's box, which is a bit lousy - printing your own copy of the map requires color, you have to remember what the colors mean, colorblindness problems, etc.  Frankly I found the color-coding confusing on first read and first look at the map; the icons for the stars use random colors not related to the color coding for the system's infrastructure quality.  They're probably supposed to relate to stellar spectrum class but that's not relevant here and we're already gone non-canonical with the random map so...  I don't know why they did that, rather than making the stars the same color as their respective planet boxes.

The lack of compatibility between Dark Nebula's maps and Traveller RPG subsector maps (both in scale and density) also highlights another oddity here - Dark Nebula is the first Traveller wargame I've read that makes no mention of integration with the RPG.  It does seem like integrating a game where turns are two years of in-universe time would be tough, but I was surprised that there was nothing.  I didn't expect much of Invasion: Earth, but we still got one good patron hook there.

What I didn't realize when I initially read Dark Nebula (not until halfway through writing this post and getting kind of suspicious that the combat system seemed much more staid than the rest of the game) was that it was a clear successor to Imperium, published in 1977.  I've only skimmed Imperium, but it looks like it shared the 2-year turn, combat system, turn structure, etc but is played on a fixed map, with slightly more complex fleet compositions including fighters and carriers, and some neat rules about armistices / inter-war periods (allowing the game to be played in a campaign fashion) and interaction between the Imperial player (playing as a frontier governor, not the emperor) and the Third Imperium.  Notably, Imperium does mostly omit tech progress and lacks neutral forces.  Like Dark Nebula, it foregoes any mention of integration with the Traveller RPG (which made more sense in 1977) and still uses the system of planetary surface boxes in adjacent empty hexes.  I may return to Imperium at some point, but given that my interest is at least nominally in RPG integration, I think it may have to wait.

My blind spot for Imperium and trying to understand Dark Nebula's place in the chronology of CT wargames also caused me to take a quick look at 1981's Fifth Frontier War.   This looks like a monster of a game, bringing together the multi-subsector scale of Imperium and Dark Nebula with some details like SDBs and percentage-based damage to units from Invasion: Earth, but with a greater eye towards RPG integration.  First and foremost, hexes in Fifth Frontier War are one parsec rather than Imperium's half-parsec, and turns in Fifth Frontier War are only one week!  But this means that it can't just abstract starship movement into "move as far as you want this turn", so you have to deal with more details.  And fixed maps allowed Fifth Frontier War to put planetary surface boxes around the edges of the board, rather than right next to the systems they're associated with (which, admittedly, might create some difficulty in locating any particular box), allowing it to increase star system density up towards that typical of Traveller RPG campaigns.  Fifth Frontier War looks tremendously ambitious and hideously fiddly, and I can't imagine why it was the last Classic Traveller boxed-set hex and counter wargame.  At the same time I salute the dream of having a metagame world-engine wargame to run concurrently with one's RPG campaign and I look forward to learning its lessons on a more thorough read/post at some point.

Classic Traveller Apocrypha: Federation and Imperium

I was sent down a bit of a Classic Traveller rabbit hole by a comment on a post over at Grognardia recently, which mentioned a CT book that I hadn't heard of before - Book 0: An Introduction to Traveller, published 1981, which I happened to have around on the Classic Traveller CD from FFE.  I haven't read it properly yet, though I did skim the sections on preparing to referee, changing the rules, and the bit mentioned in the Grognardia comment on the proposed setting:

Once the referee has decided the general features of the campaign, it is a good idea to jot down a one or two sentence summary of conditions for later reference, such as "The subsector is located on the fringe of the Moladon Federation, a loose organization of 300+ worlds governed by a federation council. Half the worlds in the subsector are in the federation, the rest are petty one or two world nations. The federation is currently in a period of stasis, between expansions, but plans to eventually absorb all worlds on its borders. The last war was over a century ago, but minor skirmishes are constantly taking place, especially between the larger outer states. Tech levels within the federation are between 5 and 12; outside they are between 1 and 9. Federation naval power is just strong enough to suppress piracy within the borders, and there is a great deal of local planetary autonomy."

This is a very different interplanetary government from the Third Imperium!  Yet it does show up in an official, GDW, Classic Traveller source.  It's also a lower tech level than I would've expected from CT's generation system; with 300 inhabited worlds, I would've expected the Moladon Federation to have at least one TL 15 world.  In order to get the distribution described, the generation rules were likely not adhered to rigorously.  Which is fine and all, but interesting to see in an official product.

The size of the proposed federation is also interesting.  At 300+ worlds, and an average of 40ish worlds per subsector, you're talking like eight subsectors - about half a sector.

This ties to something else from the Classic Traveller Apocrypha II CD - an article by Marc Miller which was originally published in the Jan/Feb 1979 issue of The Dungeoneer (which was Judge's Guild's competitor to TSR's The Dragon magazine I guess?) titled Dealing with the Concept of Empires.  FFE's Guide to Judge's Guild Traveller notes that "The first glimpses of the Third Imperium can be seen in this early article."  Dealing with the Concept of Empires describes several stages of development and coordination of interstellar empires operating under Traveller's assumption that information cannot travel faster than people (which The Concept of Empires describes as "the most basic assumption of Traveller"; Book 0, discussing changes referees might make to the rules on page 34, likewise cautions, "The speed of communication should never be allowed to exceed the speed of
travel. This is a basic tenet of Traveller..."  I hadn't seen this put so emphatically before!).

Dealing with the Concept of Empires outlines four stages for the development of an interstellar polity.  The smallest and most centralized is the federation, where all worlds are within a single jump, limited to maybe a bit over one subsector with jump-6; 60 worlds or so.  The government of a federation can project its authority and exercise state power efficiently within its whole territory.

Up from the federation is the confederation, at a two-week travel radius and with slightly weaker central authority.  This works out to 4 subsectors, or about 160 worlds under default density.  Sadly this sort of government is almost a footnote in The Concept of Empires.  This is a particularly interesting size to me in light of my observations on time, distance, language and culture for D&D; a two-week travel radius is about the size of many medieval kingdoms, and at scales larger than that I'd expect languages to start diverging.  I'm rather sad that this size of interstellar polity didn't get more attention.

Up from that is the empire, with a "communications radius" of two months, comparable to that of the Roman Empire (some quick googling also suggests that London to India was 6-8 weeks during the Age of Sail).  At jump-6, this is claimed to cover about 225 subsectors and maybe 9000 star systems.  This requires, though, that the central authority is not in "constant, immediate communication with all of its component worlds", and leaves opportunities for mercenaries, as central imperial authority is only brought to bear against exceptional threats, and cannot afford (logistically, practically) to intervene in every small local conflict that might arise within its borders.

Finally, up from the empire you have what Miller terms Imperium, where travel delays for information are so long that travel from one end of the Imperium to the other might exceed a human lifetime.  In such a situation the central authority cannot effectively govern the periphery and must cede most authority to local officials and perhaps to designated "agents", dispatched by the central authority to then wield power on its behalf at the fringes over a period of many years, "perhaps even [with] drug-induced longevity" (an interesting perspective on the level of power required for access to anagathics).  This is the premise for Miller's 2020 novel, Agent of the Imperium, following the adventures of one such agent.  This conception of an empire much too vast to administer, with delegation of authority to dispatched agents, seems to be the original vision of the Third Imperium.

Miller's closing remarks are about the possibility that the essential function of an imperium-scale government is really communications, the Imperial Postal Union.  This strikes me as a delightfully laissez-faire sort of imperial government; you can do most anything as long as you don't mess with the mail, but if you do, that's when the marines in battle-dress start taking an interest.

I think these sizings are also interesting for non-government entities.  Can a mega-corporation meaningfully run operations with more than a week or two delay in communications?  On a sufficient scale do you end up with many wholly-owned subsidiaries, each operating largely independently across their respective subsectors until an Agent of the Board arrives from HQ?

In any case - something which is surprising in the combination of these two documents, Introduction to Traveller and Dealing with the Concept of Empires, is that the proposed Moladon Federation is much too large to be a federation in The Concept of Empires' terms - "300+" planets instead of 60.  And at TL12, Moladon probably isn't using jump-6, so it should take them even longer to get to the periphery than the federation proposed in Concept.  I'm not sure what to make of this.  Concept preceded Introduction by two years.  Did something change in Miller's thinking about interstellar coordination?  Was Concept's definition of "federation" never especially canonical (probably the most likely explanation, really; it was just a magazine article, not a book).  Was it just a slip?  Has the Moladon "Federation" actually grown into a confederation or small empire in practice, but kept the old name out of tradition?  Is it more of a Stellaris-style federation, of multiple smaller interstellar governments each with high state capacity over their own one-subsector territories, all joined in a big mutual defense pact?  It's interesting to think about. 

edit: it turns out that Book 0 was written by Loren Wiseman, not Marc Miller.  So that's a pretty good explanation - maybe Wiseman never read Concept.

I did find something else interesting though while looking into the "what TL do you need for jump-6?" question.  In my previous post on jump tech level restrictions in CT Book 2, I noted that drives and powerplants for jump-6 100-ton ships are actually possible at TL 9, with the limitation on jump range for 100-ton ships really being in computers.  I was looking at the 1977 version of Book 2 and was really confused why I would have thought this, because the Jump-6 program is only size 2!  Apparently this was changed in the '81 version of Book 2, where jump program sizes now increase linearly with jump distance and jump distance is quickly bottlenecked by computers, as I had seen previously.  I think by the '77 rules, jump-6 100-ton starships were totally doable at TL-9, which is pretty wild.  But since Introduction to Traveller was published in '81, presumably for the '81 rules, this doesn't give Moladon a free pass on jump-6 at TL12.  Digging out the '81 rules instead, though, I think you only need a computer-4 to handle jump-6 plus Navigate, which is doable at TL-10.  So I guess holding together an interstellar government with J-6 X-boats is pretty doable earlier than I would've thought.  The fact that the worlds outside the Federation cap at TL-9 sort of makes sense in this light; they are the ones that don't have jump 4-6 yet and are largely stuck in their own little clusters, unable to project power very far.

Classic Traveller: Invasion: Earth Review

Invasion: Earth was published in 1981, the fifth of the series of Classic Traveller stand-alone games.  The premise is that the Third Imperium is invading Earth (defended by humans at the same tech level).  The game covers space warfare across the solar system in low detail, and then orbital bombardment, landings, and corps-scale ground warfare on a hex-map of the Earth's surface in somewhat more detail.  Turns are two weeks, with a special reinforcement turn roughly every 14 weeks, and the hex map is on an 1140 km scale.  The projection is quite neat; it's a very nice map. 

Overall verdict: very ambitious, some neat ideas, but a bit of a mess

The main pdf is 29 pages total, including the cover, front matter, rules, map, inventory of counters, counter-sheets, and combat resolution tables.  The text itself is only about 12 pages, of which two are background information on the Solomani Rim War and one and a smidge deal with using Earth in Traveller campaigns separate from the wargame.  So we really only get about nine pages of wargame rules, which is not much to cover so grand a conflict.

The rules start out relatively well with space combat, dividing the solar system into near-earth, far orbit, and deep space, and covering jumping in, closing through those distances, actually fighting, and going dark in deep space.  There is some weirdness around System Defense Boats fighting space targets; SDBs are primarily atmospheric / low orbit (I'm imagining them kind of like SSTO spaceplanes but agrav) and have only a ground bombardment attack score instead of having both a space attack score and a ground attack score like many naval units.  But because of this there's a whole separate space combat firing step just for SDBs attacking proper ships, and you have to divide up fleets being attacked by both SDBs and typical naval vessels, with part of the Imperial fleet fighting just SDBs and part fighting the regular navy. (How you divide your fleet is an interesting gameplay choice at least I guess?)  I'm not really clear why SDBs don't just have an anti-ship offensive score and use the regular combat resolution table when attacking ships, and then have a bombardment score for attacking ground targets.  Maybe it's so that they can add their bombardment score with the bombardment scores of planetary defense batteries when attacking ships doing landings?  But SDB weirdness aside, the space rules seem basically reasonable.

Atmospheric stuff like bombardment and landings follow.  There are some very weird things in this section.  Space ships in low orbit can go on overwatch against SDBs coming out of hiding in the oceans (neat) but the action economy on it is very strange, where you get to fire against each SDB wing with every naval unit on overwatch?  If the rules didn't say verbatim "All overwatch naval units attack each SDB wing that came out of hiding" I wouldn't think that that could possibly be the correct interpretation.  In the following bombardment phase, each ship or planetary defense battery only gets to attack once ("Each unit capable of firing during this phase may fire once."), but in the contested landings phase after that, planetary defense batteries can get to fire at every unit landing near them.  No saturating these air defenses up close I guess; that I can kind of buy.  But the SDB overwatch thing seems trickier to justify.

Ground combat seems fairly reasonable; units are quite mobile because antigravs are assumed to be standard kit on both sides, there's a supply system which is fairly simple and based on space-dropping logistics bases which is neat, there are stacking limits on how much stuff you can fit in a hex but this is a wargame with counters so you get some super-corps counters that refer to an off-map sheet of boxes to say "here's all the stuff that is in that hex".  There are some weird bits in the way that targets are selected during ground combat; the example of combat even provides a case where A and B are on the same side and C and D are on the other, and basically A shoots at C, C shoots at B, B shoots at D, and D shoots at A.  And apparently that's fine, there's no conception of fronts and mutual engagement with particular units who are fighting you while you're fighting them (except inasmuch as you're all in the same 1150km hex, which I guess is just a big melee of anti-gravs and plasma weapons).

Reinforcement and scoring has some interesting bits; it is assumed that the Imperial player will definitely take the Earth, and he has access to as much replacement of lost units as he wants, but taking more time and using more replacement units costs him at scoring and may cause him to lose the game even though he has taken the planet.  The actual details of reinforcement for the Solomani (hereafter Terran) player look somewhat fiddly and involve counting how many of his starting 60ish urban terrain hexes are not yet garrisoned by the Imperial player.  The game also ends when the Imperial player has occupied 50ish of those urban hexes so you need to count them to determine if the game is over, in addition to reinforcements.  The setup procedure for the Terrans to place all their starting units looks like something I might want a beer for (and I imagine the Imperial player might want a beer while he waits).

As I mentioned at the beginning, the map is neat.  Sadly the counter-sheets are quite blurry and everything that follows about the units is working from the Counter Inventory rather than the counters themselves.  (Also, I hope you like NATO symbology.  Still, would it be a proper hex-and-counter wargame without it?)  The unit variety looks painfully-high; the Terran player has nine different kinds of System Defense Boat wings, most of which have fairly small differences in stats between them.  The Imperials have lots of one-off units; for example, they get five Colonial Lift Infantry Corps at TL12 and then one at TL11 with the same nominal stats but which takes an extra penalty in combat resolution because the TL is lower.  I kind of question the inclusion of regiment-scale units with 5 combat power in a game where there are corps with 100 combat power rolling around.  Could we have just...  dropped regiments, divided all the combat power numbers by 5, and eliminated space transport capacity from cruiser squadrons?

Which is to say - there's significant room for simplification here.

(On the other hand, looking at it again, almost all of the regiment-sized units are elite, armored, or both, which means that their combat strengths are understated - they might use 5 points of transport capacity but then actually fight at strength 20)

I do appreciate that we get half a page on using this ruleset for conflicts other than this particular battle in this particular war in the Third Imperium Setting.  It mostly deals with ground troops without grav vehicles; wheeled, cavalry, and foot, and the implications on supply and sealift of not having grav vehicles be standard.   I'm here for this, it's exactly the kind of stuff that I want for mercenary involvement on Balkanized worlds in the course of a Traveller campaign, but...  there are other blockers for that.

The combat tables are mostly OK but there are some under-explained modifiers next to the Surface Bombardment Table.  It's interesting that bombardment damage on surface targets caps at 50% of the target's strength per turn - which means that splitting your fire and bombarding two targets with half of your firepower each for two turns can be more effective than concentrating it all on one target in the first turn, then the other target the next turn.  So that's a bit odd, but maybe it doesn't actually come up in play.

The material on using Earth in Traveller campaigns is basically three patrons and a couple of deeper conspiracies to tie them into.  Two were a bit trite and could happen anywhere but the third actually ties into something from the wargame so I liked that one.

Again, in conclusion - a very ambitious sort of conflict to try to tackle in nine pages of rules, and some rough edges are apparent as a result.  If anybody knows of a ruleset that is to this what Azhanti High Lightning was to Snapshot, an expanded and cleaned-up version, please let me know in the comments.

On further reflection, the other thing that this game needs is Tyranids.  It is excusable that it doesn't have them, because they may not have been invented yet when it was published, but nevertheless, it is the perfect use-case.  "How long can 50,000 guardsmen and assorted aerospace assets delay the advance of the hive fleet?  How much can they make it cost to devour this world?" are exactly the kind of questions that Invasion: Earth is aimed at answering.  This is the kind of scale that a Warhammer 40k game should be operating at.